In computer systems, two components or devices, for example, a motherboard and an internal hard disk or an external peripheral device, are connected to each other by means of physical interfaces, in order to be able to exchange data with each other. Common interfaces are, for example, the Universal Serial Bus (USB), the Small Computer System Interface (SCSI), the Serial Attached SCSI (SAS), the Serial Advanced Technology Attachment (SATA), or the Fiber Channel (FC). The transmission properties, such as, for example, the transmission rate, format and contents of individual data packets, or the addressing and communication of connected devices with each other are fixed in an associated transmission protocol for each interface.
A physical interface consists of cables, electrical conductors, and plug connections between the individual devices. The data and information are transmitted between the devices by means of analog signals that are modulated, for example, in their amplitude, in order to code digital information of individual bits. For example, a low level corresponds to the logical value “0” and a high level corresponds to the logical value “1”. Here, each device has a transmitter and also a receiver, which transmit and receive, respectively, analog signals by means of the interface in accordance with the protocol. The transmitter and receiver are here special circuits or integrated components (ICs), wherein the transmitter and receiver are often described together in one device as a so-called transceiver (transmitter and receiver). The individual circuits of the transmitter and receiver are also designated as transmitter-PHY or receiver-PHY on the basis of their task in the physical signal transmission.
A physical interface with its transmission path made from plugs, lines, and strip conductors on circuit boards influences the signal transmission between a transmitter and a receiver of two devices. Due to high-frequency scattering and electromagnetic interference, the transmitted signal is changed and distorted during the transmission on the physical interface. The properties of the transmitted signal, however, are fixed once according to the transmission protocol and are no longer changed. For error-free signal transmission, the interface is usually calibrated, as is generally known from the publication DE 10 2007 010 284 A1.
Furthermore, solutions exist for adapting the parameters of a receiver to the specification requirements according to the specified transmission protocol or for regulating the signal amplitude according to the settings of a receiver. For example, after receiving analog signals, a receiver can report to a transmitter whether the latter should increase or decrease the signal amplitude. All of these solutions, however, have the disadvantage that later adaptation or setting of a receiver or the signal amplitude allows only a limited improvement of the signal transmission.